The present invention relates to a seat ring for a valve, and more particularly to an offset or eccentric seat ring for a sanitary plug valve.
Conventional control valves are comprised of many different components. One component common to plug-type control valves is a seat ring. A seat ring primarily forms part of a flow passageway and is used in conjunction with a closure member to modify a rate of flow through the valve. In the case of a plug valve, the plug seats against the seat ring to halt or otherwise regulate flow through the valve.
In the food processing and bio-technical industries, it is common to employ valves and valve parts that promote sanitary conditions. For example, in the beer brewing industry, there are many applications for large sized sanitary control valves for brewing beer. Control valves often range from smaller sizes of one to two inches, to larger sizes of four or six inches. One conventional type of sanitary control valve is a sanitary butterfly valve. However, conventional butterfly valves have difficulty controlling fluids flowing therethrough, especially at low flow rates in large size valves.
Alternatively, eccentric rotary plug control valves provide better accuracy over a broader range of flow rates. However, these control valves are not as sanitary as the sanitary butterfly valves. A typical eccentric rotary plug control valve is illustrated in FIG. 1. A valve body 104 houses an eccentric seat ring 100. The eccentric seat ring 100 is held in place with a retainer 102. A valve plug 106 is movable within the valve body 104 and presses against the eccentric seat ring 100 to close the valve. The eccentric seat ring 100 is made eccentric, as evidenced by the eccentric seat ring 100 maintaining a cylindrical portion having a central axis 114 which is offset from a central axis 116 of the entire seat ring 100. This offset is what defines the eccentric seat ring 100.
When the valve is assembled, the eccentric seat ring 100 is placed in its approximate position, but is allowed to rotate, changing the position of the seating surface until the eccentric seat ring 100 aligns with the valve plug 106. The eccentric seat ring 100 is then secured in place with the retainer 102.
If the eccentric seat ring 100, as described in this prior art example, were to be sealed, the attempted sealing would create crevices that would not be easily cleanable during standard cleaning processes. More specifically, with reference to FIG. 1, a first crevice 108 exists between the retainer 102 and the eccentric seat ring 100, a second crevice 110 exists between the retainer 102 and the valve body 104, and a third crevice 112 exists between the eccentric seat ring 100 and the valve body 104. Fluid flowing in the direction of arrow D flows through the eccentric seat ring 100 and the retainer 102, passing over the crevices 108 and 110. Arrow D represents the flow path of a process fluid, or a cleaning fluid, through the valve body 104. Some fluid will pass into each of the first crevice 108, the second crevice 110, and the third crevice 112, and is difficult to remove.
The additional crevices 108, 110, and 112 in the eccentric seat ring 100 example require three seals, and therefore three leak potential locations for failure and bacteria growth. O-rings utilized to seal the eccentric seat ring 100 in a location to block the crevices 108, 110, and 112 create possible pooling points between the components including the eccentric seat ring 100 in crevices 108, 110, and 112. Further, the arrangement including the eccentric seat ring 100 is difficult to match to pipes because the components do not combine to conform to a particular pipe dimension. This pipe size matching is important to prevent line gasket over hang and to reduce locations for bacteria growth.
Another variation of the valve is a concentric seat ring (not shown). When the valve is assembled, the seat ring is placed in its approximate position, but is allowed to move up, down, left and right in a sliding fashion until the seat ring aligns with the valve plug. The seat ring is then secured in place with a retainer. The concentric seat valve includes similar crevices to those found between the eccentric seat ring 100 and the valve body 104. However, the sealing ability of the concentric seat valve is even further challenged during installation and alignment. Instead of rotating an eccentric seat ring, the concentric seat ring slides up, down, left, and right, to align with the valve plug. Such movement will cause a variance in the percentage of squeeze which causes an O-ring type seal to lose sealing ability.
O-rings utilized to seal the concentric seat ring in a location to block the crevices are ineffective because the O-rings will not maintain a seal when the concentric seat ring moves during assembly and/or alignment. As the concentric seat ring moves, the O-ring will not maintain a consistent percentage of squeeze, thus losing its sealing abilities. Therefore, a consistent O-ring seal cannot be maintained or guaranteed at either the concentric seat ring body, or the seat ring retainer interface. Further, the retainer also requires sealing with a seal such as an O-ring.
Standard valve cleaning processes include the use of steam and/or caustic materials, which flow through the valves to clean them out on a periodic basis. Returning to the eccentric seat ring 100 example, the steam and the caustic materials have a difficult time penetrating the first crevice 108, the second crevice 110, and the third crevice 112. The inability to penetrate results in unsanitary conditions because the crevices 108, 110, and 112 are not sufficiently cleaned. Furthermore, the presence of the crevices may generate stagnation points in the process flow, which are undesirable and can lead to bacteria growth. Alternatively, if the caustic materials penetrate into the first crevice 108, the second crevice 110, and the third crevice 112, it is very difficult to rinse the caustic materials out of the crevices 108, 110, and 112. There is a significant likelihood that the caustic materials will remain in each of the crevices 108, 110, and 112. This can cause hazardous conditions for food subsequently flowing through the valve, which can pick up the caustic material and carry it through the process to the final destination, and ultimately to a consumer.
There is a need in the art for a sanitary eccentric seat ring for use with a rotary plug valve in systems requiring sanitary conditions. The sanitary eccentric seat ring supports the ability to properly seal the seat ring in a sanitary manner to facilitate cleaning. The present invention is directed toward further solutions to address this need.
In accordance with one example embodiment of the present invention, a seat ring includes a body having a first section, a second section, and a body central axis passing through the first and second sections. A first bore is disposed within the first section, and has a first bore central axis concentric with the body central axis. A second bore is disposed within the second section, and has a second bore central axis eccentric to the body central axis.
The seat ring, in accordance with several embodiments, includes the first section being generally frusto-conical in shape. The second section is generally cylindrical in shape. The first bore within the first section is generally frusto-conical in shape, while the second bore of the second section is generally cylindrical in shape.
The seat ring can further include a flange disposed at one end of the first section. The flange is suitable for mounting the seat ring in a valve body. The flange can further include a serrated surface disposed thereon for improving the sealing properties of the flange when joined with a gasket. The flanged end of the seat ring can be modified to work with other process piping connection means, such as flangeless, triclamp, or welded ends.
In accordance with one aspect of the present invention, at least one channel is provided about a periphery of the second section. The channel is sized and dimensioned to receive at least one seal, such as an O-ring.
The arrangement of the first bore and the second bore within the first section and second section creates a structure that forms a self draining seat ring in accordance with further aspects of the present invention.
In accordance with still another embodiment of the present invention, a seat ring assembly is provided. The assembly includes a seat ring disposed in a valve housing. The seat ring includes a body having an end flange, a first section, a second section, and a body central axis passing through the first and second sections. A first bore is disposed within the first section, and has a first bore central axis concentric with the body central axis, and a second bore is disposed within the second section, and has a second bore central axis eccentric to the body central axis. The assembly further includes a sealed disposed to sealingly engage an internal wall of the valve housing. At least one fastening mechanism can be disposed on the end flange that is suitable for removably and replaceably mounting the seat ring within the valve housing. The mounting of the seat ring can occur in a manner such that the at least one fastening mechanism is remote from a flow path through the seat ring.
In accordance with still another aspect of the present invention, a method is provided of installing a seat ring. The method includes inserting the seat ring into a valve body. The seat ring has at least one seal disposed to seal a gap between the seat ring and the valve body. The method continues with rotating the seat ring to adjust a central axis of an eccentric bore within the seat ring to align with a valve control element. The seat is removably and replacably fastened into the valve body with at least one fastening mechanism, such that the at least one fastening mechanism is removed from a flow path through the valve and the seat ring.
The at least one fastening mechanism can include a clip and screw combination in accordance with one aspect of the present invention. Further, the seal can take the form of an O-ring type seal disposed about a periphery of the seat ring.